Wind turbines include a rotor driven by the wind to produce mechanical energy. The mechanical energy is converted to electrical energy and provided to a power grid, as represented in FIG. 1. The rotor and nacelle that supports the rotor among other heavy components are positioned high above the ground or sea by a support structure, typically including a tower and foundation. The nacelle and rotor may yaw about the tower to face the wind as the wind changes direction. The nacelle and rotor may also be yawed out of the wind when the wind turbine is not operating.
Wind turbine support structures may be designed with the intent that all portions of the structure have a useful service life that, at a minimum, is as long as the service life of the wind turbine, typically 20 to 25 years, when the turbine is loaded maximally. Wind turbines support structures, however, may be loaded during use in ways that cause stress and fatigue disproportionally throughout the structure.